Turkey is days away from undoing a long-standing American policy in Syria

Afrin following the capture of the Syrian city by Turkish-led forces from Kurdish militia, in March 2018. AFP

The most surprising aspect of Turkey’s conquest of Afrin is not how it ended, but how it began. In mid-January, reports emerged that the United States would set up a border force of 30,000 troops, half of them drawn from Kurdish militias.

Ankara was furious. Turkey's president Recep Tayyip Erdogan called it “a terror army” and vowed to “strangle it even before it's born”. Within hours, the US Secretary of State Rex Tillerson had pulled back, saying the situation had been “misportrayed”. But the damage was done and Turkish troops began their attack within days.

Two months on, the battle for Afrin is over. America's Kurdish allies have retreated and Syrian rebel flags are flying alongside the Turkish flag over Afrin.

Yet in itself that is extraordinary. Turkey has just openly overturned US policy – through military force, no less – while America stood by. Analysts may blame a loss of prestige dating back to Barack Obama or disengagement brought about by Donald Trump, but the reality is stark: in Syria, the US no longer gets its way.

And it may be about to get worse. Turkey is mere days away from undoing a long-standing US policy in Syria. Only the shake up in Washington and the removal of Mr Tillerson appears to have thrown a spanner into the works.

After Afrin, the gaze of Ankara has now turned to a small city in Syria that has long been the basis of US policy in that region. The city is Manbij, about 96 kilometres east of Afrin, close to the Turkish-Syria border, and the place from which the US has been supporting the Kurdish YPG (People's Protection Units) group in its battles against ISIL.

America's role in Manbij goes back a couple of years to the fight against ISIL by the previous administration. It was under Mr Obama that the US agreed to let Kurdish forces cross the Euphrates to try and push ISIL out of Manbij. At the time, US Vice President Joe Biden told Mr Erdogan that this move was temporary and promised that Kurdish troops would withdraw back across the Euphrates. That hasn't happened yet, but Turkey has not forgotten.

Ever since Turkey invaded Afrin, it has spoken openly of its intent to continue on to Manbij and clear out Kurdish troops, regardless of the US troops stationed there.

The warnings were serious enough for the US secretary of state to request a direct meeting with Turkey's president last month, following which the two sides agreed to create working groups to discuss issues around Syria and Iraq, including Manbij.

The first of those groups, on Syria, met last week in Washington and from leaked reports it appeared a significant deal had been reached. Washington would give up the YPG inside Manbij, who would withdraw across the Euphrates, and instead Turkish and US troops would jointly patrol the area. If true, it would be a significant victory for Turkey, and one that appears to have simply been handed to Ankara.

Pushing the Kurdish militias out of Manbij would please both Turkey and the Syrian rebels, but it would also have the effect of vastly weakening US plans to stay in Syria. Manbij is strategically located midway between Aleppo and Raqqa, close to the border and on the side of the Euphrates River closest to the majority of Syria's population.

Moreover the plan for joint patrols, if true, is merely window-dressing. In time, US patrols would slow down or be stopped, depending on the whims of Washington. But Turkey is there for the long-term and would seek to put its allies from among the Syrian rebels into positions of influence.

This is not mere conjecture, because Turkey has already done this elsewhere. Manbij is part of Turkey's strategy to establish a buffer zone along the border and push back the Syrian Kurds to their historical areas in the north-east.

And it is working. In the bloody chaos of the Syrian civil war, Ankara has been patient and consistent. Two years ago, Turkey and Syrian rebels took the border town of Jarablus, 40km from Manbij, from ISIL. In the months since, Turkey trained Syrian police officers, and sent Turkish medical staff, as well as facilitating reconstruction. In its own quiet way, Turkey has managed to retake a Syrian town from ISIL and repopulate it with Syrians. That far-sightedness and consistency will be difficult for the US to replicate in Manbij, which means time will be on Ankara's side.

Seen in that light, the extent of what Mr Tillerson apparently agreed is astonishing. At a stroke, the US secretary of state was willing to hand over Manbij to Ankara. Now the question is whether that policy shift will survive his replacement.

Because after Mr Tillerson was unceremoniously fired last week there has been some suggestion that Donald Trump's new appointee, former CIA chief Mike Pompeo, will take a harder line on the deal.

But short of a vast shift in focus and resources from Washington, the end result is likely to be the same. Turkey is absolutely committed to denying the Syrian Kurds control of contiguous territory along its border.

The US simply does not have the leverage to shift even the edges of the Syrian conflict in a direction it prefers, and there appears to be no appetite to invest the military and political capital required to get that leverage. Having abandoned the Kurds in Afrin, it seems to be preparing to abandon them in Manbij. Regardless of the man in the White House, Mr Obama's phrase is still Washington doctrine: Syria is still someone else's war.